Storage tube



July 21, 1959 J. BURNS ETAL STORAGE TUBE Filed Dec.

INVENTORS JOSEPH BURNS ALBE/g; EBERHARD BECKERS I. A TTORNEWS) Patented July 21, 1959 STORAGE TUBE Joseph Burns, Clifton, and Albert Eberhard Beckers, Cedar Grove, N.J., assignors to Allen B. Du Mont Laboratories, Inc., Clifton, N.J., a corporation of Delaware Application December 11, 1956, Serial No. 627,708 9 Claims. (Cl. 313-68) This invention relates to storage tubes, and more particularly to the barrier-grid type of storage tube.

Storage tubes of the above type require a target having as one element thereof, a high transparency mesh placed in close proximity to a sheet of dielectric material. The mesh must either be in intimate contact with the dielectric, or else every portion of it should be exactly the same distance away. It is difdcult to obtain either of the above conditions because the meshes usually have an inherent warp or distortion, or quickly acquire one. If the intimate contact arrangement is desired, fastening the mesh causes it to belly out in various places, thus losing contact with the dielectric. The uniform spacing embodiment is equally diflicult to achieve, since the mesh is flaccid, and tends to produce a flexing which introduces an effect similar to microphonics in an electron tube.

It is therefore the principal object of our invention to provide an improved storage tube.

It is a further object of our invention to provide an improved target for a barrier grid storage tube.

The attainment of these objects and others will be realized from the following specification, taken in conjunction with the drawings, in which,

Fig. 1 illustrates a prior art barrier grid storage tube;

Fig. 2 shows a perspective view of a fragment of our improved target; and

Fig. 3 depicts another embodiment.

Referring now to Fig. 1, it will be seen that an evacuated glass envelope has a tubular neck portion 12, a funnel shaped portion 14, and a cylindrical body portion 16. Within the neck portion 12 is an electron gun 18 which emits a stream of electrons 20. Means, not shown but well known in the art, focus and deflect electron beam 20 in a conventional manner. At the distant end of envelope 10 is a target 22, which comprises a sheet of dielectric material 24 having a metal backing plate 26 in intimate contact with the distal surface thereof.

In a manner well known to those in the art, and more fully described on pages 61-65 of Storage Tubes by Knoll and Kazan, an electrostatic charge is placed on dielectric material 24. It is one of the functions of barrier grid 28 to prevent low velocity secondary electrons from leaving dielectric 24 entirely, or from reaching some other area thereof.

Referring now to Fig. 2, there is shown in cutaway perspective form, a structure embodying the principles of our invention which eliminates the aforesaid shortcomings of the barrier grid storage tube.

Dielectric material 30 resembles a waflle, since it has pits, or depressions, in one surface thereof. One very convenient material for this structure is Photoform Glass which may be obtained from the Coming Glass Company. This type of glass is exposed through a mask to radiation of selected frequency and intensity. After suitable treating and etching of the glass, there would be produced pits of any desired depth, and of a size and shape corresponding to the apertures in the mask which was used during exposure. Square openings are preferable since they most efliciently utilize the available area.

The upper undisturbed portion of dielectric sheet 30 now has applied thereto a conductive film 31. Since this surface of the target will be exposed to electron beam bombardment, it is preferable that the conductive film does not emit secondary electrons, gold being an idealv material for this purpose. A suitable gold preparation known as Liquid Bright is a gold-containing liquid which may be poured onto a flat surface. If the side of sheet 30 having the pits is now rubbed against the surface bearing the soluble gold, the liquid will adhere to the raised portions of the dielectric material. Proper treatment, including heating, willcause the soluble gold to assume a metallic form; thus producing a gold grid 31 having meshes or openings which coincidewith the depressions in the dielectric material.

Gold is a preferable material since, being anoble' metal, it Will not contaminate the tube. Other suitable metals are silver, platinum, and palladium, all of which are available in liquids such as Liquid Bright. Alternatively, the pits may be filled, the metal deposited by spraying or some other method, and the filling removed by chemicals or heat. I

As previously explained, the remote surface of dielectric material 30 must have a backing pla-te. Our preferred arrangement is to apply a conductive coating 32 directly to its back surface; this can be either gold as described above, or any other conductive material deposited by methods which are well known.

- Alternatively, as shown in Fig. 3, a sheet of insulative material 34, such as photoform glass, may have openingsv passing entirely therethrough. A second unperforated sheet of dielectric material 36 may be placed in contiguous relation with the first perforated sheet to achieve a composite two-piece structure which is substantially the same as that shown in Fig. 2. A grid 131 is similar to the one previously described, as is backingplate-ISZ. The advantages of the embodiment shown in Fig. 3 is that dielectric material 36 may be of suitable electrical characteristics and thickness to more easily achieve unusual results.

The barrier grid storage tube may be operated in several different ways; namely, the input signal may be applied to either a control grid, the cathode, or the barrier grid; and the output signal may be obtained from the backing plate or a collector electrode. It is therefore apparent that the circuitry for operating the tube is irrelevant to our invention, as long as electrical contact can be made to the grid and backing plate. In our disclosed structure, electrical contact may be achieved by soldering or clamping to the respective elements.

In prior art tubes it was necessary to support the target on studs. Our improved target may have sections of its periphery cemented or fused to the inside of the tube wall, thus dispensing with prior art mounting means; the unfastened portions permitting evacuation of the voltmie behind the backing plate. Alternatively, our target could be hermetically sealed to the tube wall to form the end thereof.

Our invention as described above provides a unitary barrier grid target, wherein the dielectric consists of the material between the bottom of the pits and the backing layer. This thickness may be of any desired value, and will be uniform over the entire dielectric material. The grid forms an excellent, low secondary emissive barrier with a high transmission, since its openings are directly aligned with the storage elements (pits) of the dielectric material. In addition, each portion of the grid is uniformly and permanently spaced from the dielectric and the backing plate since it is part of the same structure; thus there is no possibility of the appearance of a microphonic efiect. The backing plate is also a part of the unitary target, being permanently aflixed thereto. In addition, our disclosed target comprises materials that themselves resist contamination. In cases where dust, lint, or other foreign matter becomes aflixed to the target, it is easily removed without harming the target itself. A further advantage accrues to our target, namely, it is a compact, unitary' structure which may be readily handled, cleaned, and processed.

Thus, our invention provides an improved target which obggates the prior art difiiculties of a barrier grid storage to Having described the principles and two embodiments of our invention, we desire to be limited not by the foregoing specification and illustrations, but rather by the claims granted to us.

What is claimed is: p

1. A sheet of insulative material having pits on one surface thereof; a perforated conductive film positioned on said surface, said perforations being aligned with said pits, said solid portions of said film being contiguous and in intimate contact with the unpitted portions of said surface, whereby said perforated conductive film is formed into a control grid structure which is immovably attached to a rigid sheet of insulated material, and therefore is unable to hex.

2. A combination comprising a sheet of insulative material having two substantially parallel surfaces, one of said surfaces having raised portions; a rigid inelastic grid positioned on said latter surface, said grid comprising a conductive film positioned in contiguous and intimate contact with said raised portions, whereby all parts of said grid are fixedly positioned with respect to said surface; and an inelastic conductive backing plate on the other surface of said sheet, said plate comprising a conductive material contiguous with said second surface of said sheet; whereby said grid and said backing plate are each fixedly positioned with respect to each other and with respect to said sheet, so that microphonic-type distortions are obviated.

3. A structure comprising a unitary insulated mechanical structure having openings partway therethrough, said 4 structure comprising a sheet of insulative material having perforations therethrough and a sheet of dielectric material positioned with one surface contiguous with one surface of said insulated material; a conductive film positioned contiguously in intimate contact with the other side of said perforated sheet, whereby said film is in an immovable relationship with the bottom of said opening; and a conductive backing plate contiguous with the other surface of said dielectric material, whereby said film, said structure, and said plate cooperate to form a unitary target wherein said conductive elements have an immovable relationship with the bottom of said openings.

4. The structure of claim 2 wherein said backing plate comprises a film positioned in intimate contact with said second surface.

5. The structure of claim 4 wherein said insulative material is photoform glass.

6. The device of claim 3 wherein said backing plate is a film deposited on said dielectric material.

7. A target for a barrier grid storage tube comprising: a plate of dielectric material having depressions on one surface thereof; a conductive coating of material havinga low secondary emissive characteristic positioned in contiguous and intimate contact with the undepressed portions of said surface; means for connecting an electrical circuit to said coating; a conductive film positioned in contiguous and intimate contact with the other surface of said sheet; and means for connecting an electrical circuit to said conductive film.

8. The device of claim 7 wherein said insulative material is photoform glass.

9. The device of claim 7 wherein said coating is gold.

References Cited in the file of this patent UNITED STATES PATENTS 2,548,405 Snyder Apr. 10, 1951 2,558,647 Freeman June 26, 1951 2,582,843 Moore Jan. 15, 1952 2,706,264 Anderson Apr. 12, 1955 2,788,466 Hansen Apr. 9, 1957 2,790,929 Herman et a1. Apr. 30, 1957 

